1. Field of the Invention
The present invention relates to variable length blade systems and particularly to a variable-diameter telescoping aircraft rotor system. More specifically, this invention is directed to a control and locking system and an overtravel safety stop system for variable diameter rotor blade apparatus to prevent inadvertent diameter change and to prevent overretraction or overextension of telescopic rotor blades of a helicopter. Accordingly, the general objects of the present invention are to provide novel and improved apparatus and methods of such character.
2. Description of the Prior Art
While not limited thereto in its utility, the present invention is particularly well suited for use on vertical takeoff aircraft such as helicopters. Variable diameter (i.e. variable length) helicopter rotors are known in the art. Examples of such variable diameter rotors may be found in U.S. Pat. Nos. 3,768,923 and 3,884,594, both issued to E. A. Fradenburgh and assigned to the assignee of the present invention. The full disclosures of U.S. Pat. Nos. 3,768,923 and 3,884,594 are incorporated herein by reference.
The prior art variable diameter rotor systems include an outer airfoil shaped blade which is caused to translate to telescope with respect to an inner blade portion or torque tube by jackscrew action. A traveling nut on the jackscrew is connected to the translatable blade so that the outer blade moves with the traveling nut. Clockwise or counterclockwise rotation is imparted to the jackscrew shafts via a differential gear arrangement located in the rotor head. The differential includes pinion gears coupled to each jackscrew shaft and upper and lower bevel gears which are coupled, via coaxial drive shafts, respectively to retraction and extension control brakes or clutches. When neither retraction or extension of the rotor blades is desired, the bevel gears of the differential and thus the coaxial shafts will all rotate about the rotor axis at the speed at which the rotor is being driven. Should it be desired to change the diameter of the rotor, one of the coaxial drive shafts will be braked thus producing a speed differential between the bevel gears and thereby imparting either clockwise or counterclockwise rotation to the differential pinion gears coupled to the blade jackscrews.